Upgrading tiger and leopard to snow leopard

Firstly, my apologies if this question has already been answered elsewhere, I did search for it but couldn't find it.

I have a Macbook running Leopard and an iMac running Tiger. I am looking to upgrade Leopard to Snow Leopard and Tiger to Leopard.

If I were to purchase Snow Leopard and install it on the Macbook, would I then be able to use the copy of Leopard that came with the Macbook on the iMac? I am not trying to use 2 copies of the same thing on different machines, I just want to put a new os on one machine and move the existing one to another.

I am reluctant to purchase the Mac Box Set version of Snow Leopard for the iMac because I do not want or need iLife and iWork.

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